Today after I changed my oil I went to start my car, and it would turn over really, really slow. It had happened before, and then immediately fired up, so I kept cranking (really stupid) All of a sudden a bunch of smoke came pouring out from under the hood. I stopped cranking (of course) and popped the hood, and it was a wire burning. It wasn't the big ground wire connected to the alternator bracket, but the other little one connected to the body. Lesson learned - always tighten the big ground cable down very good. By the way, what is this smaller wire? Just a secondary ground?

 

The little one is a chassis ground. For all the stuff that grounds to the body..... (just and insurance policy basically.)

 

You didn't actually disconnect the battery to do an oil change, did you?